A linear trap, which allows execution of MSn spectrometry inside, is widely used for analyses such as proteome analysis. Hereinafter, the explanation will be given below concerning how the mass-selective ejection of ions trapped in the linear trap has been performed in prior arts.
An example of the mass-selective ion ejection in a linear trap is disclosed in U.S. Pat. No. 5,420,425. After ions injected from the axial direction have been accumulated inside the linear trap, the ion isolation or ion dissociation is performed depending on requirements. After that, a supplemental AC field is applied between a pair of mutually-opposed quadrupole rods, thereby making it possible to excite specific ions in the radial direction. Then, the excited ions are mass-selectively ejected in the radial direction by scanning a trapping RF voltage. A pseudo harmonic potential, which is generated by a quadrupole field in the radial direction, is used for the mass separation. This condition allows implementation of high mass resolution.
Also, an example of the mass-selective ion ejection in a linear trap is disclosed in U.S. Pat. No. 6,177,668. After ions injected from the axial direction have been accumulated, the ion isolation or ion dissociation is performed depending on requirements. After that, a supplemental AC voltage is applied between a pair of mutually-opposed quadrupole rods, thereby exciting the ions in the radial direction. Then, the ions excited in the radial direction are mass-selectively ejected in the axial direction by a Fringing Field which occurs between the quadrupole rods and an end lens. Frequency of the supplemental AC voltage, or amplitude value of a trapping RF voltage is scanned. A pseudo harmonic potential, which is generated by a quadrupole field in the radial direction, is used for the mass separation. This condition allows implementation of high mass resolution. In the vicinity of the central axis, influence by the RF voltage is small, and thus ejection energy is low.
Also, an example of the mass-selective ion ejection in a linear trap is disclosed in U.S. Pat. No. 5,783,824. Accumulation of ions injected from the axial direction is performed. Vane lenses are inserted between quadrupole rods. A harmonic potential is generated along the linear-trap axis by a DC bias between the vane lenses and the quadrupole rods. After that, the ions are mass-selectively ejected in the axial direction by applying a supplemental AC voltage between the vane lenses. Voltage of the DC bias or frequency of the supplemental AC voltage is scanned. In the vicinity of the central axis, influence by a RF voltage is small, and thus ejection energy is low.
In U.S. Pat. No. 6,504,148, the disclosure has been made concerning a method of locating the linear trap disclosed in U.S. Pat. No. 6,177,668, and after that, of locating a collision cell and a time-of-flight mass spectrometer. In principle, this method allows a significant enhancement in Duty Cycle of precursor ion scan or neutral-loss scan.
In U.S. Pat. No. 6,483,109, the disclosure has been made concerning a method of locating the linear traps disclosed in U.S. Pat. No. 5,783,824 in large numbers in tandem, and thereby enhancing Duty Cycle of the ions. In this method, the accumulation, isolation, and dissociation of the ions are performed in the different linear traps in parallel. As a result, in principle, this method allows a significant enhancement in the Duty Cycle.
Patent Document 1: U.S. Pat. No. 5,420,425
Patent Document 2: U.S. Pat. No. 6,177,668
Patent Document 3: U.S. Pat. No. 5,783,824
Patent Document 4: U.S. Pat. No. 6,504,148
Patent Document 5: U.S. Pat. No. 6,483,109